There has been proposed a technology in which, in a case where a terminal device belongs to a LAN (abbreviation for Local Area Network) and a user inputs the IP addresses of a plurality of information devices connected to the LAN, the terminal device transmits the plurality of inputted IP addresses to a registration server on internet. The registration server notifies the number of received IP addresses to a management server on the internet, and receives a PIN (abbreviation for Personal Identification Number) code from the management server. Then, with respect to each of the plurality of IP addresses, the registration server generates a URL (abbreviation for Uniform Resource Locator) including the corresponding IP address and the PIN code. Subsequently, the registration server transmits the plurality of generated URLs to the terminal device. In the case where the user selects a URL from the plurality of URLs, the terminal device transmits a PIN code including the selected URL to an information device having the IP address included in the selected URL. If the information device receives the PIN code from the terminal device, it transmits a connection request including the PIN code to the management server. If the PIN code is authenticated in the management server, the information device receives a token from the management server. As a result, the information device can perform communication with the management server, using the token.